Manual rocking of carriages is bothersome, tiring and time-consuming. In order to solve this problem, a variety of mechanical rocking devices have been developed and are known in the patent literature.
U.S. Pat. No. 2,649,167 to Strom, for example, discloses a spring motor for rotating a centrifugal weight adapted to be attached to a crib, chair, playpen or the like, in order to impart thereto a vertical rocking or oscillating motion.
U.S. Pat. No. 2,916,745 to Lesk discloses a mechanism for affixing under the mattress of a crib including an electric motor power drive means and arm construction for rotating an eccentrically disposed weight.
U.S. Pat. No. 3,311,935 to Petty discloses a bed vibrating device including a vertically mounted eccentrical weight arranged to be secured to the grid springs of the crib and impart a vertical motion thereto. The motor rotating the weight must be an AC motor which operates on the wall current.
U.S. Pat. No. 2,980,108 to Scott discloses a pulsating mattress including a spring assembly which is caused to vibrate by a motor driving a shaft having an eccentrically mounted weight thereon.
Similarly, U.S. Pat. No. 3,934,283 to Raffel discloses a device for connecting to any bed frame including two vibratory motors which produce interfering vibratory waves to set up differential vibrations in the bed frame.
U.S. Pat. No. 2,805,427 to Edgmon discloses a crib having means for providing longitudinal motion thereto comprising a crib bottom supporting plate and eccentric weight means to vibrate the plate.
All of these devices require manual activation and stopping. Each is relatively large and heavy and requires a large quantity of energy (which is generally supplied by the wall current). In each, except Lesk, the motor produces vertical vibration of the crib or the like.